Woolworths, Coles, Aldi: Why it pays to check docket

WHEN you go shopping, do you casually throw your receipt in with the groceries, neglecting to read it over?

Or, worse, do you decline to print one out and walk away, ignorant what you've paid for all those carefully-selected items?

If you answered "yes", you could be ripping yourself off, with scanning errors causing supermarkets to overcharge for everyday items - and many shoppers failing to detect, or act upon the mistakes to recoup what they are owed.

A survey of 2,141 Australians by comparison site finder.com.au found that two in five people had been overcharged at the till in the past year.

But one-quarter said they didn't bother checking their dockets and, of those who did, they would only bother going for a refund if they were overcharged by more than $10.

Finder's money expert Bessie Hassan said it was up to shoppers to spot mistakes and challenge errors.

"You might be left out of pocket and not even realise," she said.

"An advertised discount might fail to be applied or an item might scan twice - whatever the reason, shoppers get overcharged all the time."

A payment processing glitch caused Woolworths customers to be charged double for their purchases, prompting the retailer to apologise and reverse the transactions.

While the mistake was not with the retailer in this case, scanning errors are a more common than some may realise - and shoppers may be entitled to more than just a partial refund.